Beginners	Built-In Functions	Advanced	CGI Applications
Introduction Syntax Operators Variables Scope Data Types Flow Control Subroutines RegEx	Arithmetic Strings Arrays Hashes Date/Time Printing	Files Directories Databases Reports RegEx Exceptions System Calls Modules One Liners Reference	Unix Forms CGI Cookies

Hash Functions Summary
Manipulation of hashes is one of Perl's strong points. The hash functions can be categorized roughly into four areas, depending on how they manipulate or return information about hashes.

Access Elements	keys, values, each
Delete Elements	delete
Test	exists

Hash Functions Reference
Here's a quick reference of the available hash functions, in alphabetical order.

• delete - deletes a key/value pair

      delete EXPR
  
      delete $hash{$key}   
      

• each - retrieves the next key/value pair

      each HASH
  
      while (($key,$value) = each %ENV) {
  	print "$key=$value\n";
      }  
      

• exists - test whether a hash key is present

      exists EXPR
  
      print "Exists\n" 	if exists $hash{$key};
      

• keys - retrieve list of keys from a hash

      @result = keys %ENV
      

• values - retrieve list of values from a hash

      $result = values %ENV
      

Hash Code Snippets
The following code shows several methods of manipulating arrays.

     foreach $key (keys %myhash) { print "$key: $hash{$key}\n" }
     while (($key,$value) = each (%myhash)) { print "$key: $value\n" }

     %myhash = ()              # clear a hash
     delete ($myhash{$key})    # remove key/value pair
     if exists $myhash{$key}  # test for existence of a key

If you have suggestions or corrections, please let me know.